1. Field of the Invention
This invention relates to a driving-force transmitting part, and an electrophotographic photosensitive drum, a process cartridge and an electrophotographic image forming apparatus using the driving-force transmitting part.
Here, the electrophotographic image forming apparatus refers to an apparatus for forming an image on a recording medium by the use of the electrophotographic image forming process, and the term “electrophotographic image forming apparatus” covers an electrophotographic copier, an electrophotographic printer, (a laser printer, an LED printer or the like), a facsimile apparatus, a word processor or the like.
Also, the process cartridge may refer to charging means, developing means or cleaning means and an electrophotographic photosensitive drum integrally made into a cartridge which is made detachably mountable to the main body of the image forming apparatus. Alternatively, the process cartridge may refer to at least one of charging means, developing means and cleaning means and an electrophotographic photosensitive drum integrally made into a cartridge, which is made detachably mountable to the main body of the image forming apparatus. Further alternatively, the process cartridge may refer to at least developing means and an electrophotographic photosensitive drum integrally made into a cartridge, which is made detachably mountable to the main body of the apparatus.
2. Description of the Related Art
In image forming apparatus using the electrophotographic image forming process, there has heretofore been adopted a process cartridge system in which an electrophotographic photosensitive member and process means for acting on the electrophotographic photosensitive member are integrally made into a cartridge, which is made detachably mountable to the main body of the image forming apparatus. According to this process cartridge system, maintenance of the apparatus can be done by a user himself without resorting to a serviceman and therefore, the operability of the apparatus could be markedly improved. So, this process cartridge system has been widely used in the image forming apparatuses.
In an image forming apparatus to which such a process cartridge is detachably mountable, a driving device is disposed in the main body of the image forming apparatus, and a driving force is transmitted in each process means of the process cartridge through driving-force transmitting means. As such driving-force transmitting means, Japanese Patent Applications Laid-Open No. 08-328449 proposes means as shown in FIG. 11 of the accompanying drawings, wherein as a method, a driving shaft 100 formed with a twisted-polygonal recess 101 (in the shown example, a twisted-polygonal hole having a substantially equilateral triangular cross-section) is provided on the image forming apparatus side, and as shown in FIG. 10 of the accompanying drawings, a first flange 210 is formed with a twisted-polygonal prism-shaped protrusion 211 (in the example of FIG. 10, a twisted equilateral triangular prism having a substantially equilateral triangular cross-section) as driving-force transmitting means, and the protrusion 211 is inserted in the recess 101 to thereby transmit the driving force.
In the driving device, the transmission of the driving force is effected from the recess 101 to the protrusion 211 inserted in the recess 101 and therefore, the driving side and the driven side are normally in contact with each other and it becomes easy to improve the accuracy of rotation. Also, the vertices of the protrusion 211 tend to equally contact with the inner surface of the recess 101 and therefore, the axes are aligned with each other. Further, the two have the twisted shapes and therefore, forces act on the recess 101 and the protrusion 211 in a direction to attract them to each other and thus, the positioning of the photosensitive drum in the lengthwise direction thereof becomes easy.
In such an apparatus as previously described, the driving force transmitted to the first flange 210 is transmitted to a developing roller 41 shown in an embodiment of the present invention through a gear portion 213 provided on the flange, and to a transfer roller 70 through a second gear portion 221. In the example of the conventional art, a fit-sliding portion 212 is provided so as to protrude from the end surface perpendicular to the axis of the first gear portion 213. The fit-sliding portion 212 is fitted to and supported by a bearing provided in a cartridge frame.
The construction described in the aforementioned publication is practically very excellent as a driving system for an electrophotographic photosensitive drum.
The present invention is a further development of the conventional art proposed in the aforementioned Japanese Patent Application Laid-Open No. 08-328449.